Figure 3. Differences among cells in different layers of the multilayer Itgb1 mutant lung epithelium.

(A) Whole-mount (left column) and section (right column) in situ hybridization of E13 lungs showing that the expression of Bmp4 remains restricted to the distal branching epithelium in the Itgb1^CKO/−; Shh^Cre/+ mutant, and that only cells on the basal side, but not on the lumenal side (arrowhead), of the multilayer epithelium in the Itgb1^CKO/−; Shh^Cre/+ mutant lung express Bmp4. Scale bar, 100 um. (B) Section immunostaining of E13 lungs showing that cleaved Caspase-3 (CASP3), a marker of apoptosis, is preferentially expressed by cells located on the lumenal side of the multilayer epithelium in the Itgb1^CKO/−; Shh^Cre/+ mutant lung. Nuclei were counter-stained with DAPI. The dashed lines demarcate the basal side of the lung epithelium. Scale bar, 50 um.